Metal matrix composites of titanium base have been used for high load bearing applications such as in aircraft and high compression diesel engine parts. Ceramic materials are preferably used in these composites serving as a reinforcing element. The desirability of these metal-ceramic composites lies largely in such properties as low density, high tensile strength, high fracture resistance, high temperature stability, and low thermal conductivity.
The metal-ceramic composites retain the most desirable properties of each of its component material, i.e., the low density, low thermal conductivity, and high temperature stability properties of the ceramic and the high tensile strength and high fracture resistance properties of the metal. These metal matrix ceramic composite materials when compounded properly possess the best properties of both the component materials. To achieve the optimum properties of the metal matrix ceramic composites, the processing conditions for the alloys and the thermal cycling treatment of the alloy for dimensional stability must be carefully performed.
Numerous titanium metal composites have been proposed by others. Authors Certificate USSR 556191 to Glazunov, et al. discloses a widely used titanium composite of Ti-6Al-4V. Glazunov, et al. further discloses another composition of Ti-5.5Al-2Sn-2Zr-4.5V-2Mo-1.5Cr-0.7Fe-0.2Cu-0.2C. The tensile strength of this alloy approaches 1400 MPa while the relative elongation approaches 10%.
European patent application EP 0243056 to Barber discloses titanium-based alloys and methods of manufacturing such alloys. The discloses by Barber is Ti-7Al-7Zr-2Mo-10Ge. Barber also discloses a based alloy in general consisting of 5.0-7.0% aluminum, 2.0-7.0% zirconium, 0.1-2.5% molybdenum, 0.01-10.0% germanium and optionally one or more of the following elements: tin 2.0-6.0%, niobium 0.1-2.0%, carbon 0-0.1% and silicon 0.1-2.0%; the balance being titanium. It should be noted that molybdenum and germanium are two necessary elements in Barber's composition.
U.S. Pat. No. 4,915,903 to Brupbacher, et al., U.S. Pat. No. 4,195,904 to Christodoulou, and U.S. Pat. No. 4,915,905 to Kampe, et al. discloses a process for stabilization of titanium silicide particles within titanium aluminide containing metal matrix composites. While the patents cite the necessity of having zirconium present to stabilize the titanium silicide in order to prevent it from dissolving in the matrix, the titanium silicide phase is in a matrix of titanium aluminide, not titanium. The patents further suggest that titanium silicide particles would be highly unstable within a titanium environment.
Author Certificate USSR 1501170 to Mazur, et al. discloses a titanium composite containing 2.0-7.0% molybdenum, 2.0-5.0% aluminum, 4.0-8.0% silicon, and 0.5-1.5% manganese.
Crossman, et al. discloses titanium compositions containing 10% zirconium and 8% silicon. Metallurgical Transactions, 1971, Vol. 2, No. 6, p. 1545-1555. Crossman, et al. used induction melting and electron beam melting techniques to produce their unidirectionally solidified eutectic composites which included 7.7 volume percent of TiB and 31 volume percent of Ti.sub.5 Si.sub.3 fibers for reinforcement. However, the mechanical properties of Ti-10Zr-8Si were not reported.
Zhu, et al. studied the silicides phases in titanium-silicon based alloys. Material Science and Technology, 1991, Vol. 7, No. 9, p. 812-817. Zhu, et al. studied the distribution, type, composition, in a lattice parameters of the silicides in cast titanium alloys of Ti-4.0Si-5.0Al-5.0Zr. Zhu, et al. did not study any titanium composites containing more than 4% silicon.
Flower, et al. studied silicide precipitation in a number of martensitic titanium-silicon alloys and ternary and more complex alloys containing zirconium and aluminum. Metallurgical Transactions, 1971, Vol. 2, No. 12, p. 3289-3297. In titanium composites containing zirconium and aluminum, the maximum content of silicon studied was 1.0%.
Horimura discloses in Japanese patent publication 3-219035 a titanium base alloy for high strength structural materials made of 40 to 80% atomic weight titanium, 2 to 50% atomic weight aluminum, 0.5 to 40% atomic weight silicon, and 2 to 50% atomic weight of at least one of nickel, cobalt, iron, manganese, or copper.
It is therefore an object of the present invention to overcome the various drawbacks associated with the use of prior art titanium composites.
It is another object of the present invention to provide a titanium matrix composite having eutectically formed titanium-ceramic reinforcement therein.
It is yet another object of the present invention to provide a titanium matrix composite having eutectically formed titanium-ceramic reinforcement therein comprising more than 9% by weight silicon.
It is a further object of the present invention to provide a titanium matrix composite comprising titanium-based solid solution and reinforcing phases of titanium-ceramic.
It is another further object of the present invention to provide a titanium matrix composite having eutectically formed titanium-ceramic reinforcement therein whereby the alloy elements are selected from the group consisting of silicon, germanium, aluminum, zirconium, molybdenum, chromium, manganese, iron, boron, nickel, carbon, and nitrogen.
It is yet another further object of the present invention to provide a family of titanium matrix composites incorporating titanium matrix for its high tensile strength and high fracture resistance properties and titanium-ceramic reinforcement for its low density and low thermal conductivity properties such that the composite material has the best properties of both components.
It is still another further object of the present invention to provide a method of achieving property optimization for a titanium matrix composite having eutectically formed titanium-ceramic reinforcement therein comprising titanium, silicon, aluminum, and at least one element selected from the group consisting of zirconium, molybdenum, chromium, carbon, iron and boron by thermal cycling the composite between the temperature of 800.degree. C. and 1020.degree. C. for a minimum of 30 cycles.